Film-pressure plate or pad for photographic cameras



April 16, 1929 A. J. DENNlss ET AL 1,709,782

FILM PRESSURE IILATE OR PAD FSOR PHOTOGRAPHIC CAMERAS f` Filed Ap-r`i:l 14, 1927 5 Sheets-Sheet l A. J. DENNlss ET AL 1,709,782

FILM PRESSURE PLATE OB PAD FOR PHOTOGRAPHIC CAMERAS April 16, 1929.

Filed April 14, 1927 5 Sheets-Sheet lino April 16, 1929.

A. DENNISS ET AL FILM PRESSURE PLATE OR PAD FOR PHOTOGRAPHIC CAMERAS Filed April 14, 1927 5 Sheets$heei Patented .sip-r. l5, i929.

UNITED STATES PATENT OFFICE.

ALFRED JOSEPH DE1\TNTSS,1`JFv CI-IINGFORD, AND" VALENTNE WLLIAM EDWARDS, OF WALTHAMSTOVW, LONDON, ENGLAND, ASSIGNORS TO THE HOUG-HTON--BUTCHER MAN"UFACTT TRINGrl COMPANY LIMITED, OF LONDON7 ENGLAND, AN ENGLISH LIMITED LIABILITY COMPANY.

FILM-PRESSURE PLATE 0R PAD FOR PHOTOGRAPHIG CAMERAS.

Application led April 14, 192'?, Serial No. 183,804, and in Great Britain October 29, 192,6.

rlhis invention relates to roll lm pliotographic camerasin which va pressure device such as a springloaded plateor pad employed to hold the sensitive film flat in the focal plane is provided With means operable from outside the camera back to press the spring loaded plate or pad downA upon the film, and also to release the pressure when the film is to be moved from one exposure to the next. In such an arrangement, if the pressure is maintained on the film by omittingto operate the freeing device scratches oi' striations may be made on the filmV as it is Wound along. An object ofthe present invention is to provide a construction in which this possibility of error on'the part of the operator is reduced or eliminated.

According to the present invention,l the externally operable freeing device for the pressure plate or pad is constructed and arranged in such a manner that it covers the ruby Window (or aperture through which the exposure number is ordinarily visible) at such time as the pressure plate or padis pressed upon the film. Thus before the operator can `Watch for the appearance ofthe Ynew exposure number, he must release the pressure ony the-film by moving the operating device Yaway from the ruby Window thereby releasing the pressureV on the film.

A general form of construction in' accordance with the present invention consists in mounting` the pressure plate or pad on a flat or leaf spring normally acting to Withdraw the pressure plate or pad from .contact with the film, various devices being employed to act kupon the spring or the pressure plate or pad to thrust the latter down upon the film when an exposure is to be made. The type of operating means employed Will vary according to the construction'of the camera.

Examples of suitableforms of construetion in accordance With the inventionY are illustrated in the accompanying drawings, in

Fig. k1 is a sectional plan on the line 1-.1 Fig. 2 of a box camera embodying one form of construction according to this invention7 the pressure plate being sheWn in operative position against the'film.

Fig. 2 is a rear elevation partly in section, and

Fig. 3 is a local cross section on the line V3 3 Fig. 2 of the same construction, Fig. 3

shewing the pressureplate released.

Fig. 1 is a rear elevation, Fig. 5 a local section on the line 5v5 Fig.

4, and

Fig. 6 a local section on the line 6 6 Fig.

l ofvan alternative form ofconstruction applied to a box camera.

Figs. 7 and 8 are respectively a local rear elevation and a section on the line 8 8 Fig.

spring 14C, the plate 12 being preferably somewhat loose on the rivet to enable the pressure of the plate -to be distributed evenly on the film 15 which passes across the usual frame 16 inthe focal plane and against Which itis held When the pressure plate is Lthrust inwards. The spring 14 isfrigidly secured at one end to the camera back 17 by a screw 18 (see Fig. 3) the other end being` provided with a slot 19 to alloW longitudinal movement.

Rigidly secured to the spring is a stud 20 entering a hole in the camera back and acted upon by an inturned nose 21 of a lever 22 pivoted to a plate 23 screwed tothe outside of the camera back. The free end of the lever 22 is provided With a plate 2li adapted to cover the usual ruby Window when lthe lever is flat upon the camera back and the pressure plate 12 is in contact With the film asin Figs. 1 and 2.

To release the pressure, the lever is lifted camereJ beck, e cam projection on said rod enga-ging thc leef spring in such e manner that the manipulation of seid lever in one direction forces the pressure pla-te into contact with the lilni und in tlie other direction allows the pressure plate to be retracted by the spring to release the iilm, a part of said actuating lever being positioned so as to cover the aperture through which the eX- posure number is ordinarily visible et yeuch 10 time as the pressure plate is pressed against the hn and to uncover said aperture when the Elm is released.

ALFRED JOSEPH DENNISS. VALENTINE WILLIAM EDWARDS. 

